British Pat. No. 1,236,875 discloses the herbicidal utility of a number of S-alkyl substituted 1-(disubstituted piperidine carbothioates) including S-isopropyl-1-(5-ethyl-2-methylpiperidine carbothioate), which is included in that patent as compound No. 4. As stated in the British patent, the piperidinyl ring is a rigid structural system and therefore the compounds described therein may exist in various stereochemical conformations, particularly cis and trans configurations.
As shown in the British patent, the compounds of this type had been found to be effective herbicides. S-isopropyl-1-(5-ethyl-2-methylpiperidine carbothioate) had been found to be a particularly effective herbicide and tests showing its herbicidal activity had been conducted, both on a small screen basis, and in cotton fields. Results of these tests are on pages 6 and 7 of the British patent.
It has now been found that the herbicidal activity of this compound is affected by the presence or absence of its cis isomer. More specifically, it has been found that the herbicidal effect of a mixture of cis and trans isomers of S-isopropyl-1-(5-ethyl-2-methylpiperidine carbothioate), preferably one containing at least about 20% of the cis isomers, and most preferably containing between about 60 and about 65% of the cis isomer, is remarkably and unexpectedly different from that of the trans isomer alone.
A method of using such a formulation comprises applying an herbicidally effective amount thereof to the area where control is desired. Such a formulation has been found to be especially effective in the control of undesirable vegetation in the presence of specific beneficial vegetation, especially in the presence of cotton.
An herbicide as used herein means a substance which controls or modifies the growth of plants. By an herbicidally effective amount is meant an amount of substance which causes a modifying effect upon the growth of plants. Such modifying effects include all deviations from natural development, for example, killing, retardation, defoliation, desiccation, regulation, stunting, tillering, stimulation, dwarfing and the like. By "plants" is meant germinant seeds, emerging seedlings and established vegetation including the roots and above-ground portions.